Protein comprises a significant portion of a balanced diet of animals. Traditionally, the protein component for the young animal's diet has been supplied by milk or milk products. However, the cost of milk products has led to the search for alternate proteins from other sources to replace in whole or part the milk protein used in diets of the young animal. Due to its low cost and availability, the soybean has been used as source of protein in the diet of the young animal. Unfortunately, some species of animals, including preruminant calves, typically become allergic to the soy flour; it is believed that they become allergic to two major storage proteins, glycin and .beta.-conglycinin, present in conventional soy flour. When conventional soy flour is fed to calves, many calves develop an allergic response to the soy flour or more particularly to components of the soy flour such as glycin and .beta.-conglycinin. Such calves suffer loss of appetite, poor growth, low weight gain and diarrhea. Ingestion of conventional soy flour typically produces digestive abnormalities including changes in the rate of movement of digesta in the abomasum and small intestine, increased gut permeability to protein macromolecules, inflammation of the intestinal mucosa and high concentrations of circulatory IgG antibodies to glycin and .beta.-conglycinin. Other species of young animal, including the human infant, the pig, rat, mouse and chick have also been shown to develop allergies to these proteins.
Efforts have been made to remove or inactivate the allergenic components in soy products. One process which involves extracting soy flour with alcohol and water, produces a product known as soy "concentrate." Unfortunately this process is expensive and removes a substantial portion of the valuable carbohydrate component of the soy flour. The soy concentrates also do not suspend well in water.
Another process involves separating the soy flour protein into multiple protein fractions. These products, known as "isolates," may still contain antigenic proteins, and have also had most of the carbohydrates of the soybean removed. Moreover, animals still develop allergies to some isolates and the isolates are expensive.
It is desirable to have a process which provides a soy product, particularly soy flour, that does not induce diarrhea, poor growth or weight loss in the recipient animal, does not remove other nutritionally valuable components of the soy flour and is less expensive than conventional soy products.